Nitrogen Containing Organic Compounds

1. Amines

1.1 Classification of amines

• Primary amines: contain one alkyl or aryl group bonded to the nitrogen atom (RNH₂).
• Secondary amines: contain two alkyl or aryl groups bonded to the nitrogen atom (R₂NH).
• Tertiary amines: contain three alkyl or aryl groups bonded to the nitrogen atom (R₃N).
• Aliphatic amines: amines in which the nitrogen atom is bonded to at least one aliphatic carbon atom.
• Aromatic amines: amines in which the nitrogen atom is bonded to an aromatic ring.

1.2 Methods of preparation of amines

• Reduction of nitro compounds: Nitro compounds can be reduced to primary amines using a variety of reducing agents such as hydrogen gas (H₂) over a metal catalyst, iron (Fe) or tin (Sn) and hydrochloric acid (HCl), or sodium borohydride (NaBH₄).
• Ammonolysis of alkyl halides: Alkyl halides can be reacted with ammonia (NH₃) to form primary, secondary, or tertiary amines, depending on the number of alkyl groups on the alkyl halide.
• Hofmann bromamide degradation: Amides can be converted to primary amines through the Hofmann bromamide degradation reaction, which involves the reaction of an amide with bromine (Br₂) in aqueous sodium hydroxide (NaOH) solution.

1.3 Physical and chemical properties of amines

• Basicity: Amines are basic due to the presence of the lone pair of electrons on the nitrogen atom. The basicity of an amine increases with the number of alkyl groups attached to the nitrogen atom.
• Hydrogen bonding: Amines can form hydrogen bonds with other molecules, such as water, due to the presence of the lone pair of electrons on the nitrogen atom.
• Solubility: Amines are generally soluble in water due to their ability to form hydrogen bonds. The solubility of an amine decreases with the number of alkyl groups attached to the nitrogen atom.
• Nucleophilic substitution: Amines can undergo nucleophilic substitution reactions, in which the lone pair of electrons on the nitrogen atom attacks a positively charged carbon atom.

1.4 Reactions of amines

• Nucleophilic substitution: Amines can undergo nucleophilic substitution reactions with alkyl halides, acyl chlorides, and other electrophiles.
• Acylation: Amines can react with acyl chlorides to form amides.
• Alkylation: Amines can react with alkyl halides to form quaternary ammonium salts.
• Hinsberg test: Amines can be distinguished from other nitrogen-containing compounds using the Hinsberg test. The Hinsberg test involves reacting the amine with benzenesulfonyl chloride and then treating the product with aqueous sodium hydroxide.

2. Amides

2.1 Structure and bonding in amides

• Amides contain a carbonyl group (C=O) bonded to a nitrogen atom (N).
• The carbon-nitrogen bond in an amide is a double bond, and the nitrogen-hydrogen bond is a single bond.
• Amides are polar molecules due to the difference in electronegativity between the carbon and nitrogen atoms.

2.2 Methods of preparation of amides

• Reaction of carboxylic acids with ammonia or amines: Carboxylic acids can react with ammonia or amines to form amides. The reaction is catalyzed by a strong acid, such as hydrochloric acid (HCl) or sulfuric acid (H₂SO₄).
• Ammonolysis of acid chlorides: Acid chlorides can react with ammonia or amines to form amides. The reaction is catalyzed by a Lewis acid, such as aluminum chloride (AlCl₃) or iron(III) chloride (FeCl₃).

2.3 Physical and chemical properties of amides

• Polarity: Amides are polar molecules due to the difference in electronegativity between the carbon and nitrogen atoms.
• Solubility: Amides are generally soluble in water due to their ability to form hydrogen bonds. The solubility of an amide decreases with the number of carbon atoms in the molecule.
• Hydrogen bonding: Amides can form hydrogen bonds with other molecules, such as water, due to the presence of the polar carbonyl group.
• Hydrolysis: Amides can be hydrolyzed to form carboxylic acids and ammonia or amines. The hydrolysis reaction is catalyzed by a strong acid, such as hydrochloric acid (HCl) or sulfuric acid (H₂SO₄).
• Reduction: Amides can be reduced to form amines. The reduction reaction is typically carried out using a reducing agent such as lithium aluminum hydride (LiAlH₄) or sodium borohydride (NaBH₄).
• Nucleophilic substitution: Amides can undergo nucleophilic substitution reactions with strong nucleophiles, such as hydroxide ion (OH^-) or alkoxide ion (RO^-).

3. Nitriles

3.1 Structure and bonding in nitriles

• Nitriles contain a carbon-nitrogen triple bond (C≡N).
• The carbon-nitrogen bond in a nitrile is a polar bond due to the difference in electronegativity between the carbon and nitrogen atoms.

3.2 Methods of preparation of nitriles

• Dehydration of amides: Amides can be dehydrated to form nitriles using a strong dehydrating agent, such as phosphorus pentoxide (P₂O₅) or thionyl chloride (SOCl₂).
• Reaction of alkyl halides with cyanide ion: Alkyl halides can react with cyanide ion (CN^-) to form nitriles. The reaction is typically carried out in a polar aprotic solvent, such as dimethylformamide (DMF) or acetonitrile (CH₃CN).

3.3 Physical and chemical properties of nitriles

• Polarity: Nitriles are polar molecules due to the difference in electronegativity between the carbon and nitrogen atoms.
• Solubility: Nitriles are generally soluble in water due to their ability to form hydrogen bonds. The solubility of a nitrile decreases with the number of carbon atoms in the molecule.
• Hydrogen bonding: Nitriles can form hydrogen bonds with other molecules, such as water, due to the presence of the polar carbon-nitrogen triple bond.
• Hydrolysis: Nitriles can be hydrolyzed to form carboxylic acids and ammonia. The hydrolysis reaction is catalyzed by a strong acid, such as hydrochloric acid (HCl) or sulfuric acid (H₂SO₄).
• Reduction: Nitriles can be reduced to form amines. The reduction reaction is typically carried out using a reducing agent such as lithium aluminum hydride (LiAlH₄) or sodium borohydride (NaBH₄).
• Nucleophilic addition: Nitriles can undergo nucleophilic addition reactions with various nucleophiles, such as water (H₂O), alcohols (ROH), and ammonia (NH₃).

4. Diazonium Compounds

4.1 Structure and bonding in diazonium compounds

• Diazonium compounds contain a positively charged nitrogen atom (N⁺) bonded to two aryl groups.
• The nitrogen-carbon bonds in a diazonium compound are polar covalent bonds due to the difference in electronegativity between the nitrogen and carbon atoms.

4.2 Methods of preparation of diazonium compounds

• Diazotization reaction: Diazonium compounds can be prepared by reacting an aromatic amine with nitrous acid (HNO₂). The reaction is typically carried out in a cold, acidic solution.

4.3 Physical and chemical properties of diazonium compounds

• Stability: Diazonium compounds are generally unstable and can decompose easily to form nitrogen gas (N₂) and a carbocation.
• Solubility: Diazonium compounds are soluble in water due to the presence of the positively charged nitrogen atom.
• Reactivity: Diazonium compounds are highly reactive and can undergo a variety of reactions, such as electrophilic aromatic substitution, coupling reactions, and azo dye formation.

4.4 Reactions of diazonium compounds

• Electrophilic aromatic substitution: Diazonium compounds can undergo electrophilic aromatic substitution reactions with a variety of nucleophiles, such as phenol